import eachOf from './eachOf.js'
import withoutIndex from './internal/withoutIndex.js'
import wrapAsync from './internal/wrapAsync.js'
import awaitify from './internal/awaitify.js'

/**
 * Applies the function `iteratee` to each item in `coll`, in parallel.
 * The `iteratee` is called with an item from the list, and a callback for when
 * it has finished. If the `iteratee` passes an error to its `callback`, the
 * main `callback` (for the `each` function) is immediately called with the
 * error.
 *
 * Note, that since this function applies `iteratee` to each item in parallel,
 * there is no guarantee that the iteratee functions will complete in order.
 *
 * @name each
 * @static
 * @memberOf module:Collections
 * @method
 * @alias forEach
 * @category Collection
 * @param {Array|Iterable|AsyncIterable|Object} coll - A collection to iterate over.
 * @param {AsyncFunction} iteratee - An async function to apply to
 * each item in `coll`. Invoked with (item, callback).
 * The array index is not passed to the iteratee.
 * If you need the index, use `eachOf`.
 * @param {Function} [callback] - A callback which is called when all
 * `iteratee` functions have finished, or an error occurs. Invoked with (err).
 * @returns {Promise} a promise, if a callback is omitted
 * @example
 *
 * // dir1 is a directory that contains file1.txt, file2.txt
 * // dir2 is a directory that contains file3.txt, file4.txt
 * // dir3 is a directory that contains file5.txt
 * // dir4 does not exist
 *
 * const fileList = [ 'dir1/file2.txt', 'dir2/file3.txt', 'dir/file5.txt'];
 * const withMissingFileList = ['dir1/file1.txt', 'dir4/file2.txt'];
 *
 * // asynchronous function that deletes a file
 * const deleteFile = function(file, callback) {
 *     fs.unlink(file, callback);
 * };
 *
 * // Using callbacks
 * async.each(fileList, deleteFile, function(err) {
 *     if( err ) {
 *         console.log(err);
 *     } else {
 *         console.log('All files have been deleted successfully');
 *     }
 * });
 *
 * // Error Handling
 * async.each(withMissingFileList, deleteFile, function(err){
 *     console.log(err);
 *     // [ Error: ENOENT: no such file or directory ]
 *     // since dir4/file2.txt does not exist
 *     // dir1/file1.txt could have been deleted
 * });
 *
 * // Using Promises
 * async.each(fileList, deleteFile)
 * .then( () => {
 *     console.log('All files have been deleted successfully');
 * }).catch( err => {
 *     console.log(err);
 * });
 *
 * // Error Handling
 * async.each(fileList, deleteFile)
 * .then( () => {
 *     console.log('All files have been deleted successfully');
 * }).catch( err => {
 *     console.log(err);
 *     // [ Error: ENOENT: no such file or directory ]
 *     // since dir4/file2.txt does not exist
 *     // dir1/file1.txt could have been deleted
 * });
 *
 * // Using async/await
 * async () => {
 *     try {
 *         await async.each(files, deleteFile);
 *     }
 *     catch (err) {
 *         console.log(err);
 *     }
 * }
 *
 * // Error Handling
 * async () => {
 *     try {
 *         await async.each(withMissingFileList, deleteFile);
 *     }
 *     catch (err) {
 *         console.log(err);
 *         // [ Error: ENOENT: no such file or directory ]
 *         // since dir4/file2.txt does not exist
 *         // dir1/file1.txt could have been deleted
 *     }
 * }
 *
 */
function eachLimit(coll, iteratee, callback) {
    return eachOf(coll, withoutIndex(wrapAsync(iteratee)), callback);
}

export default awaitify(eachLimit, 3)